Vehicle engines may include turbochargers, or superchargers configured to force an increased amount of air mass into an engine's intake manifold and combustion chamber by compressing intake air with a turbine compressor. In some cases the compressor may be driven by a turbine configured to capture energy from a flow of exhaust gas from the engine. In transient and steady state operation of compressors, there are known noise, vibration, and harshness (NVH) issues characterized by a whoosh noise, or simply whoosh. The whoosh condition may cause undesirable or unacceptable levels of NVH, and may also lead to turbocharger/engine surge. In particular, turbochargers including a compressor with a ported shroud casing experience issues with noise resulting from a blade pass frequency (BPF) of an impeller of the compressor.
Attempts have been made to mitigate noise from turbocharger compressors. One attempt includes providing small channels to disturb a boundary layer of an incoming fluid flow field to the turbocharger. Another attempt to mitigate noise is disclosed in US Patent publication 2010/0098532 to Diemer et al. Diemer et al. attempts to reduce turbocharger stall noise by providing a groove that straddles a leading edge of splitter blades of the compressor. The groove is located downstream from a leading edge of main blades to provide a path for fluid around a rotating stall.
Other attempts to minimize compressor noise have provided various re-circulation passages wherein part of the flow is re-circulated from a downstream position to an upstream position via a passage separate from a main flow passage. One example of such an approach is disclosed in U.S. Pat. No. 7,942,625 to Sirakov et al. Sirakov provides a bleed passage downstream from a blade leading edge that enables a portion of fluid flowing through the compressor to re-circulate to an upstream location via an internal cavity and injection passage.
However, the inventors herein have recognized potential issues with such systems. As one example, these approaches fail to investigate compressor fluid flow path in an area of the main blade leading edge, and they also fail to effectively address whoosh noise. Additionally, these approaches do not target a broadband frequency range of whoosh noise with minimal effect on the fluid flow field, and they do not specifically address the issue of noise resulting from the blade pass frequency of the compressor impeller.
In one example, the issues described above may be addressed by a compressor, comprising: a casing; a flow passage formed by an interior surface of the casing; a compressor wheel located in the casing downstream of the flow passage and having at least one main blade; a resonance chamber formed within the casing, surrounding the flow passage, and fluidly coupled to the flow passage via a recirculation passage and a bleed passage; and an aperture formed between the resonance chamber and the flow passage, and coupled to the flow passage between the recirculation passage and the bleed passage. As one example, the compressor may additionally include a flow disrupting feature formed by the flow passage and the aperture may be one of a plurality of apertures. The flow disrupting feature may include a change in cross sectional area of the flow path that when located at the leading edge of the main blades of the compressor may decrease whoosh. Additionally, embodiments may include components of a flow disrupting feature that may be sized and proportioned in accordance with a particular mathematical formula which relates the components in a specified way to one or more particular frequencies of whoosh noise. In this way, the combination of the flow disrupting feature and the apertures may disrupt the flow path of air through the compressor and a broad band frequency range defined by whoosh can be targeted, thereby reducing a noise level produced by the compressor.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.